Ice bag palletizer

ABSTRACT

An automatic pallet stacking machine for loading bags of ice cubes onto a pallet has a first infeed conveyor with a pick and turn device for orienting the bags, and a collating conveyor adjacent a pallet holder or pallet elevator where the bags are accumulated until a row of bags is formed. Then a gantry picks up the bags and places transports the row to the pallet. The pick and turn device and the gantry employ vacuum heads that have closed cell foam side walls to accommodate the lumpy and shifting nature of the bag contents. A programmable controller ensures that the bags rows are formed in appropriate patterns so that the bags in each tier interlock with the bags in the tier beneath.

BACKGROUND OF THE INVENTION

This invention concerns automated arrangements for stacking items onto a pallet, and is more particularly concerned with apparatus for palletizing bags or sacks of loose articles, such as ice cubes. In particular, the invention is concerned with machines that line up the bags of ice cubes or similar articles into rows of bags in predetermined patterns, and that move the rows of bags onto the pallet, and then after each layer or tier is completed, move the pallet down for stacking the next layer or tier.

The invention is also concerned with technology for lining up and turning the bags as need be so that the bags will be placed in a row pattern onto an indexing conveyor or collation conveyor, and is concerned in particular with technology that employs vacuum systems capable of achieving a desired stacking pattern by control of the various vacuum pickups and conveyors. The invention concerns pallet stacking apparatus that employs a vacuum pickup device which picks up a number of bags of articles at one time, i.e., a row of the bags, and positions them onto a pallet. The invention here relates also to vacuum pickups having special vacuum cups adapted to work with bags of products that might be lumpy or prone to shifting, such as ice cubes.

The present invention also concerns technology that can be employed as pallet counterbalance systems that increases in force as the pallet is loaded and is moved down.

Moreover, the invention concerns arrangements in which a pallet loader may be situated between two pallet holders, so the bags can be stacked onto one pallet while, on the other side, a full pallet can be taken away and replaced with an empty pallet.

The current method of palletizing bags of ice cubes requires stacking them manually onto a pallet. This involves having an individual assigned to a pallet station near an ice bagging machine. The machine inserts ice cubes into a polyethylene bag, seals the bag, and transports the bags to the pallet station at a rate of about 30 to 40 bags per minute. The bags are lifted by hand and placed on the pallet in alternating patterns so that the bags in each tier interlock with the bags in the tier beneath. This is difficult and strenuous work, and it is often difficult to find and keep reliable employees willing to do this.

There have been a number of examples of automated palletizing equipment proposed, for such items as boxes or cartons, of for bags of more or less granular material such as sand or concrete mix. However, because ice cubes are lumpy and create an irregular top surface of the bag, those previously proposed systems do not offer a palletizing solution for automatically stacking bags of ice cubes.

One example of bag palletizing equipment is provided in Marth et al. U.S. Pat. No. 4,024,965. That equipment is relevant to the general concept of orienting and stacking bags to form layers or tiers on a pallet in a pallet elevator. There is an infeed conveyor, and an intermediate conveyor at a bag diverting station, and a row-forming station which is comprises a plurality of rollers. Marth et al. employs a sweep bar assembly for moving the bags onto a pallet in a pallet elevator.

There are examples of equipment that employ vacuum lifting devices for moving or orienting bags or cartons of product. Typical vacuum lifting features are shown in Goodman U.S. Pat. No. 6,003,296, which has a vacuum pick-and-place feature that can change the orientation of a bag. Thibault U.S. Pat. No. 4,242,025 employs a rotatable sucker head on a horizontally movable carriage. Padgin et al. U.S. Pat. No. 2,841,433 and Wahl et al. U.S. Pat. No. 2,716,497 show mechanisms for orienting articles on a pallet, and stacking two pallets alternately. Sheehan U.S. Pat. No. 3,921,825 shows a mechanism for bag turning using vacuum cups. However, none of these prior proposals address the problem of lifting and turning bags of lumpy, shifting articles, nor of transporting such bags from a row forming position to a position on a pallet.

As for the general concept of orienting items for the purpose of stacking them on a pallet, Bon U.S. Pat. No. 4,984,963 shows a stacker that is programmable for article orientation, and which employs a drop-down pallet elevator using pneumatic cylinders. Pearce et al. U.S. Pat. No. 4,753,564 relates to a device that stacks tiers of articles onto pallets, employing a mechanism for feeding fresh pallets and also having a vertical pallet elevator mechanism with chain drive.

Jones U.S. Pat. No. 3,780,884 employs a pallet holder that retracts as it is loaded. Miller, Jr. U.S. Pat. No. 3,164,080 shows a drop-down pallet elevator, with a bag orienting and stacking feature.

The current state of the art does not provide orienting, lifting, transporting, or stacking equipment that can accommodate the articles in the nature of bags of ice cubes. The state of the art does not provide vacuum heads that are adapted for picking up and maintaining a vacuum on bags of lumpy shifting product. The state of the art lacks a combination of a primary or infeed conveyor and a staging or collating conveyor, and lacks an effective pick-and-turn mechanism, i.e., lift mechanism for turning either 90 or 180 degrees, so as to orient the bags properly and in an appropriate pattern for stacking. The state of the art lacks a torsion-spring-based counterbalance for the pallet elevator which increases in spring force with the increasing weight of the pallet as it is filled. The state of the art does not suggest a convenient, small-footprint solution for an automated ice-bag pallet stacker, and does not suggest apparatus that is especially adapted for automatically stacking bags of ice cubes.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide apparatus for stacking bags of ice cubes or other like product and which overcomes the drawbacks of the prior art.

It is another object to provide an ice bag palletizer that arranges the incoming bags into rows of predetermined patterns, and then transports the rows of bags onto the pallet to form layers or tiers of bags, and then continues to arrange the bags into rows and to transport them such that the successive tiers of bags on the pallet interlock one another.

It is a further object to provide a vacuum lift mechanism with vacuum lift heads that conform to the irregular surfaces of the bags of ice cubes.

A still further object is to provide the palletizer equipment with a pallet lift mechanism that increases in lift force as the pallet is filled, with the weight of the pallet being shared between a spring mechanism and a motor drive mechanism.

Yet another object is to provide apparatus that permits continuous operation with one pallet being stacked while another is removed and replaced with a fresh pallet.

In accordance with one aspect of the present invention, pallet stacking apparatus are provided for automatically stacking bags filled with solid objects, which may have an irregular, lumpy, shape and may be shifting in nature, such as bags of ice. These filled bags are stacked automatically onto a pallet in layers or tiers of predetermined patterns of rows. In the apparatus, a pallet holder e.g., a pallet lift or elevator, holds a pallet at a predetermined position. A collating conveyor, i.e., an indexing or staging conveyor, is situated adjacent the pallet holder. An infeed conveyor receives the filled bags from a source, i.e., an ice bagging machine, and carries these bags towards the staging conveyor. Above the staging conveyor there is a pick-and-turn mechanism, i.e., an orienting mechanism that is adapted to pick up the bags of ice cubes and rotate them selectively for ninety degrees (to orient the bags into a transverse position) or for one-hundred eighty degrees (to displace the bags by the width of the bag). This is operated under control of a process controller so that the filled bags will form the rows with a predetermined row geometry when the bags collect on the staging conveyor. This ensures the bags of ice will be in the proper orientation when they are positioned onto the pallet for each given layer or tier on the pallet.

The collating or staging conveyor collects the bags to form each row. The bags are blocked or barred at the end of the conveyor with the bags being held in place until a complete row has been accumulated or collected on the staging conveyor. A bag transport mechanism, i.e., a vacuum head shuttle or gantry, picks up each complete row of filled bags from the staging conveyor when the row is complete, and transfers the row to a predetermined position on the pallet.

The pallet lift or elevator holds the pallet at a predetermined elevated position adjacent the staging conveyor, and incorporates a mechanism for lowering the pallet incrementally as each layer of bags is completed. Favorably, this mechanism includes a torsion spring mechanism such that the spring force on the pallet increases with each increment that the pallet is lowered. The pallet holder also has a motor drive for raising and lowering the pallet, with the load being shared by the torsion spring and the motor.

In one preferred version, the conveyors are belt conveyors, and the staging or collating conveyor has a belt with a low-friction surface that permits sliding of the bags.

The orienting mechanism or pick-and-turn device can be a rotary vacuum arrangement, in which a rotary arm or frame is positioned over the infeed conveyor, and has a pair of vacuum heads attached onto it. The rotary arm and vacuum heads can be raised and lowered for picking up the bags, and can be selectively rotated through either 90 degrees or 180 degrees for changing the orientation of the bags. A presence sensor can detect when a bag of ice is under the pick-and-turn device, and interrupts motion of the infeed conveyor belt while the device acts to change the orientation of the ice bag.

Favorably, the vacuum heads can be formed with a rigid cap portion and an annular skirt or side wall that is attached onto the cap portion and extends down from it. The skirt may be formed of a flexible resilient material, e.g., a closed-cell foam elastomer, so that the skirt deflects to conform with irregularities in the top surface of the bags. This enables the vacuum head to maintain vacuum despite the irregular and shifting nature of the ice cubes or other items in the plastic bags.

A bag transport mechanism lifts and carries completed rows of bags from the staging conveyor to the pallet. This may comprise a set of rails that are situated above the pallet holder and span across pallet and the staging conveyor. A shuttle or gantry, i.e., a transport assembly, is mounted to travel along the set of rails. The transport assembly has an array of vacuum heads disposed on it and adapted to pick up the row of filled bags. These vacuum heads hold the bags while the transport assembly travels to a position over the pallet, and then release the ice bags onto the pallet. In one favorable implementation, the bag transport mechanism includes twelve heads arranged in two rows of six heads. The raising and lowering of the heads and the application of suction are controlled by the system controller, and that vacuum can be applied selectively either to only one of the two rows of heads or to both of the rows of heads. This permits the rows of bags to be configured and transported as a row of three bags end to end, a row of six bags arranged transversely, or a row of bags of mixed orientation.

As in the pick and turn device, the transport mechanism vacuum heads are favorably each formed with a rigid cap portion and an annular skirt or side wall that depends from the cap portion with the skirt member being formed of a flexible resilient elastomer, such as a rubber-like closed-cell foam that conforms to irregularities in the upper surface of the bags.

The above and many other objects, features, and advantages of this invention will be more fully appreciated from the ensuing description of a preferred embodiment, which is to be read in conjunction with the accompanying Drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic side elevation of the ice bag palletizer according to one preferred embodiment of this invention.

FIG. 2 is a schematic front elevation of this embodiment.

FIG. 3 is a perspective view of this embodiment.

FIG. 4 is a perspective view of another embodiment.

FIG. 5 is an assembly view of a vacuum head employed in these embodiments.

FIG. 6 is a sectional view of the vacuum head.

FIG. 7 is a sectional view of the gantry and vacuum heads of the foregoing embodiment(s) shown lifting bags of ice cubes or the like.

FIG. 8 illustrates the stacking scheme carried out by these embodiments in achieving interlocking tiers or layers of the ice cube bags stacked onto the pallet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference now to the Drawing, and initially to FIGS. 1, 2 and 3, an ice bag palletizer arrangement 10 according to the present invention is shown adjacent an ice cube bagging machine 12, which here can be for example a Hamer ice packaging form fill and seal machine in any of various models. In FIG. 3, some of the structure is omitted. In this example, the ice cube bags and seals the ice cubes into polyethylene bags at a rate of about 40 bags per minute, with each bag being 7 to 8 pounds of ice and having length and width dimensions of about sixteen by nine inches. The bags of ice cubes drop down to a discharge conveyor 14 that carries the filled bags to an incline conveyor 16, which carries the bags up to an elevation of about six feet, to feed them to the ice palletizing arrangement 10.

An infeed conveyor 18 receives the ice cube bags, and is in the form of a low profile belt conveyor, 48 inches in length and 24 inches in width, with a belt formed of a polyurethane-coated canvas. This belt can be a cleated belt with quarter-inch cleats on three-inch centers for a good coefficient of friction. The infeed conveyor has a belt speed of about 167 feet per minute, to provide adequate gap or spacing between successive bags, so the bags can be picked and placed, as described shortly.

A sensor 20, here in the form of a cantilevered sensor arm and SPST switch, is placed at the top side of the infeed conveyor 18 to detect when a bag is present. This sensor 20 is coupled to a programmed logic controller or PLC that is located in a controller cabinet 22 (FIG. 2), and the PLC will interrupt movement of the infeed conveyor belt to permit a pick and place operation, after which the belt will resume action.

A pick-and-rotate device 24 is situated above the infeed conveyor 18 for picking up the ice cube bags and rotating them either 90 degrees or 180 degrees on the infeed conveyor. The device has a pair of vacuum heads 26, i.e., vacuum cups, mounted on a rotatable frame. There is an associated centrifugal regenerative blower 28 to provide vacuum to these vacuum heads 26, with a valve 30, controlled by the PLC, to switch between atmospheric pressure and suction, and a vacuum hose or conduit 32 linking the valve 30 to the vacuum heads or cups 26. The device may also be configured to pick up and displace the bags linearly, rather than rotate them through 180°, i.e., to side-shift the bags.

When the sensor 20 detects that a bag is present, but belt of the conveyor 18 stops momentarily; the pick-and-rotate device descends and picks up the bag, and then rotates through either ninety or one-hundred-eighty degrees, as determined by a program in the PLC. Some of the bags are permitted to pass through without being picked up or rotated. The bags are initially presented on the infeed conveyor belt in a lengthwise fashion, i.e., with the shorter ends front and back, and to one side of the centerline of the belt. The pick and rotate device 24 turns the bags ninety degrees to orient them in a transverse fashion, i.e., with the shorter sides to right and left of the belt, and rotates them one-hundred-eighty degrees to locate them in a straight on or lengthwise fashion, but oriented to the other side of the belt centerline. Alternately, the pick and rotate device 24 can side shift the bags or displace them laterally. The action of the device 24 allows the bags to be lined up into rows of three bags end-to-end lengthwise, six bags transversely side-by-side, or six bags with a mixed orientation, so that the bags can be placed into tiers on the pallet with the bags of each tier interlocking with the bags in the tier beneath.

After the bag is released from the device 24, the bag travels to the next stage, which is a collation conveyor 38 or indexing conveyor.

The collation conveyor 38 here is a low profile belt conveyor, also 48 inches in length and 24 inches in width, similar to the infeed conveyor, but the belt here contains polyester-impregnated fibers. This belt may also be a cleated belt with one-quarter inch cleats on thirty-six inch centers.

A photosensor 40 detects when each bag has been transferred to the collation conveyor 38. This is used to control the advancing of the conveyor 38, to advance the bags after they have passed the pick and turn station. There is a barrier 42 at the far or distal end of the belt of the conveyor 38, so that the bags are held on the collation conveyor until a full row has been formed. That is, the collation conveyor 38 indexes the bags until the full row (three bags or six bags) has been collected. In this embodiment, the pattern for each row, as aforesaid, can be three bags end-to-end, six bags side-by-side, or six bags mixed orientation. This will be described in detail later on.

A linear motion gantry 50 is situated above the collation conveyor 38 and is in the form of a frame that is mounted to travel upon a pair of transverse tracks 52 (see FIG. 3). The gantry 50 is movable from the position over the conveyor 38 to positions over a pallet holder 54, which in this embodiment, is situated immediately adjacent the conveyor 38. The gantry carries a plurality of vacuum heads or vacuum cups 56, which are of similar construction to the vacuum heads 26 described earlier. Here there are twelve vacuum heads 56 arranged in two rows of six heads each. In this arrangement, two heads 56 are positioned over each bag for lifting and carrying the rows of bags. There is a regenerative blower 58 to provide suction to the vacuum heads of the gantry 50, a suction line 60, and dual valves 62, one of which is switched between atmosphere and suction, and the other of with selects between applying suction to just one of the two rows of heads or to both rows of heads, depending on whether the row of bags consists of three or six bags.

It should be mentioned here that there are air cylinders to move the gantry up and down and transport motors to drive the gantry transversely, but these are not shown specifically here so as to avoid some drawing clutter. Likewise, the air cylinders and motors associated with the pick and turn device 24 are omitted from the drawing.

The pallet holder 54 is here in the form of a vertical, four-sided enclosure, and this holds a standard pallet 64 on which bags 66 of ice cubes are stacked. The pallet 54 is somewhat oblong, and so the bags 66 fit five across in one direction, and six across in the other direction. This means that in this example the bags 66 of seven to eight pounds of ice cubes are stacked in tiers of two rows of six and one row of three, i.e., fifteen bags per tier, and the pallet 54 holds twenty tiers. The tiers are stacked in successive patterns that alternate from one tier to another so that the bags of each tier overlap and interlock the bags of the other tiers so that the bags 66 remain securely in place on the pallet 64.

The pallet holder 54 contains a pallet lift or elevator 68 for raising the pallet and then lowering the pallet as the bags 66 are stacked onto it. There are chain drives 70 located within corner posts 72 of the pallet holder, and a torsion spring 74 coupled to these chain drives. The torsion spring charges when the pallet drops down, so that its spring force increases as the pallet 64 is filled and drops down. The torsion spring balances about fifty percent of the weight of the pallet as the ice cube bags 66 are stacked onto it. Also, a motor drive 76 is coupled with the pallet lift to provide the remainder of the force necessary to raise and lower the pallet 64. The motor drive is controlled by the PLC in the control cabinet 22. When the pallet is empty (e.g., when it is loaded into the pallet holder) the torsion spring will lift the empty pallet to the top. The pallet 64 then drops down incrementally as it is loaded until it is finally situated at the bottom of the pallet holder 54 (as shown in FIG. 2). An access door 78 is provided on the forward side of the pallet holder to permit the loaded pallet to be removed and replaced with a fresh pallet. This door 78 is provided with interlocks and safety features such as a flashing lamp to indicate locked and open states of the door. The PLC will interrupt operation of the bag machine 12 and the palletizing arrangement 10 until the door 78 is closed and latched and the fresh pallet 64 is brought to the top position to receive the bags.

FIG. 4 shows an alternative embodiment, in which the infeed conveyor 18 and collation conveyor 38 are situated between a pair of pallet holders, including a first pallet holder 54 on the right and a second pallet holder 154 on the left. The gantry 50 here is situated upon a pair of extended tracks so that the gantry can travel from the home position over the conveyor 38 to positions over either of the two pallet holders 54, 154. The bags 66 are loaded alternately into the pallets in the two pallet holders, first loading bags 66 onto the pallet 64 in the one holder 54 and then loading onto the pallet in the second pallet holder 154. In this arrangement, the bags of ice cubes 66 are loaded continuously, i.e., without interruption, with the loaded pallet being removed from the one pallet holder and replaced with fresh pallet while the ice cube bags are being loaded and stacked onto the pallet in the other pallet holder. In this arrangement, there is no need to interrupt the bagging and stacking operations when the operator is removing the full pallet and then replacing it with a fresh, empty pallet.

Details of the vacuum heads or cups 26 or 56 are shown in FIGS. 5 and 6. Here each vacuum head is formed of a rigid cap 80 or top in the form of a round or circular member, e.g., a disk or dome. This may favorably be formed of a PVC or other durable rigid or semirigid plastic resin. An opening or socket 82 is formed centrally on the cap 80, which serves for mounting the vacuum head onto the associated gantry or pick and turn device, and also for communicating with the associated suction conduits to supply suction to the vacuum head(s). Affixed onto the outer rim of the cap 80 is a skirt 84 or side wall formed of a durable but soft, flexible closed cell foam polymer, i.e., a foam rubber. This foam material will deflect and conform to the irregular shape of the top surfaces of the ice cube bags 66, so that the vacuum cups will maintain continuous suction onto the bags during the pick and turn operation and during gantry transport. The foam material of the vacuum head sidewalls 84 accommodates the general lumpiness of the contents of the bags 66 as well as the tendency of the contents to shift when the bags are being moved. This material maintains suction even under the reduced temperature condition associated with the making, bagging, and stacking of ice. As shown in FIG. 7, a pair of the vacuum heads 56 of the gantry 50 are shown, each lifting an end of a respective ice cube bag 66. In this embodiment, the cap 80 is about three inches in diameter, and the closed cell foam rubber sleeve or sidewall 84 is about three inches in height with a wall thickness of about one inch.

FIG. 8 illustrates generally the row forming and stacking procedure according to one embodiment of the invention, where the bags 66 proceed (i.e., along the conveyor 18), are picked up and turned by the pick and turn device 24, and are either rotated ninety degrees, rotated one-hundred-eighty degrees, side-shifted, or not turned, as programmed in the programmable logic controller.

In this example, a row 90 is formed of six bags 66 in a pattern of mixed orientation, i.e., two end bags placed transversely and the middle four bags arranged in pairs oriented longitudinally. This row 90 is then picked up by the gantry 50 and transported (to the right in this view) and placed in the position shown in ghost lines to form a tier of bags indicated as 96 a. Here, there are already two previously formed rows 92 and 94, respectively of three bags arranged longitudinally, and of six bags arranged transversely. Below this tier of fifteen bags there is an earlier formed tier 96 b where the three respective rows of bags 90, 92, and 94 are in a different order of row patterns, and below that another tier of bags 96 c with the bags in a different order of row patterns 92, 94, 90. The bags 66 are thus stacked so that the bags in each tier overlap the bags in the tier beneath, and interlock with them to create stability in the stack on the pallet. Other patterns could be used for this purpose, and where the bags are of a different size, i.e., for ten pound bags or twenty pound bags, the rows can be formed in different arrangements as well.

The palletizing arrangement of this invention has a relatively small footprint, of about five feet by five feet, and seven and a half feet in height. One attendant can operate more than one of these palletizing machines, and in addition can attend to moving the full pallets into the ice warehouse and loading the fresh pallets. No human lifting is needed in stacking the ice bags 66. The count of bags on each pallet is consistent, and the pallets of bags have an improved integrity over hand-stacked ice bags.

In addition to the ice bag palletizer(s) as discussed above, principles of this invention can be used favorably for stacking other packages onto pallets or carriers, e.g., bags of crushed rock or other irregular items. In some cases, the gantry and pallet holder can be arranged for movement of the rows of bags in the distal direction rather than transversely as in the above-described embodiments. The row patterns can be changed as needed depending on bag size, pallet size, and other factors. In some embodiments, the gantry can be configured for swing motion rather than only linear motion.

Although the preferred embodiment has been employed in connection with automated stacking of bags of ice cubes in predetermined patterns onto a pallet, it is possible to employ the principles of this invention in other environments. The pallets can be stacked automatically where the product handling generates airborne particulates which could create a health hazard for a human attendant doing hand stacking.

While the invention has been described with reference to a specific preferred embodiment, the invention is certainly not limited to that precise embodiment. Rather, many modifications and variations will become apparent to persons of skill in the art without departure from the scope and spirit of this invention, as defined in the appended claims. 

1. Apparatus for automatically stacking bags filled with solid objects onto a pallet in layers of predetermined patterns of rows of the filled bags; comprising: a. a pallet holder for holding the pallet in a predetermined position; b. a staging conveyor positioned adjacent said pallet holder; c. an infeed conveyor receiving the filled bags from a source thereof and carrying the same to the staging conveyor; d. an orienting mechanism aligned with said infeed conveyor for selectively lifting and turning said filled bags; e. control means for controlling the orienting mechanism so that the filled bags are presented from the infeed conveyor to said staging conveyor such as to form rows of said bags in said predetermined patterns; f. said staging conveyor including means for holding said bags in place until a complete row thereof has been accumulated on the staging conveyor; and g. a bag transport mechanism for picking up each row of filled bags from said staging conveyor when the row is complete and for transferring same to a predetermined position on said pallet.
 2. The apparatus of claim 1, wherein pallet holder includes a pallet lift for holding the pallet at a predetermined elevated position adjacent said staging conveyor, and means for lowering the pallet incrementally as each layer of bags is completed.
 3. The apparatus of claim 2, wherein said pallet holder includes a torsion spring mechanism which increases the spring force on the pallet with each increment that the pallet is lowered.
 4. The apparatus of claim 3, wherein the pallet holder includes a motor drive for raising and lowering said pallet.
 5. The apparatus of claim 1, wherein said infeed conveyor includes a belt having a surface that permits sliding of said bags thereon.
 6. The apparatus of claim 1, wherein said orienting mechanism includes a rotary arm positioned over said infeed conveyor, a pair of vacuum heads positioned on said rotary arm, and means for raising and lowering the rotary arm and for selectively rotating the same for 90 degrees and for 180 degrees.
 7. The apparatus of claim 1, wherein said orienting mechanism includes means for displacing the bags to one side without rotating them.
 8. The apparatus of claim 6, wherein said vacuum heads are each formed with a rigid cap portion and an annular skirt member that depends from the cap portion and is formed of a flexible resilient material that conforms to irregularities in the surface of the bags.
 9. The apparatus of claim 8, wherein said skirt member is formed of a closed-cell foamed elastomeric material.
 10. The apparatus of claim 1, wherein said bag transport mechanism comprises a set of rails disposed above said pallet holder and spanning across said pallet and said staging conveyor; a transport assembly that is mounted to travel along said set of rails; and a set of vacuum heads disposed on said transport assembly to pick up the bags in a row of said bags and to hold same while the transport assembly travels to a position over said pallet, and to release said bags onto said pallet.
 11. The apparatus of claim 10, wherein said set of vacuum head on said bag transport mechanism includes twelve heads arranged in two rows of six heads; and the transport mechanism includes means for controlling the application of vacuum to the heads, such that vacuum can be applied selectively to either of the two rows of heads or to both of the rows of heads.
 12. The apparatus of claim 1, wherein said vacuum heads are each formed with a rigid cap portion and an annular skirt member that depends from the cap portion and is formed of a flexible resilient material that conforms to irregularities in the surface of the bags.
 13. The apparatus of claim 12, wherein said skirt member is formed of a closed-cell foamed elastomeric material. 